System and method for providing filter/mixer structure for OFDM signal separation

ABSTRACT

Apparatuses and methods of manufacturing same, systems, and methods to separate out a target numerology from a mixed numerology signal are described. In one aspect, a three mixer, two filter (3M2F) structure can separate out any one of multiple possible target numerologies. In another aspect, a sampled signal is frequency rotated such that one end of the target numerology is within one end of a passband of a first filter and a second filter, filtered by the first filter which attenuates any signal past the one end of the passband, frequency rotated again such that the opposite end of the target numerology is within the opposite end of the passband, filtered by the second filter which attenuates any signal past the opposite end of the passband, and frequency rotated a third time such that the target numerology returns to its original location in the frequency domain in the sampled signal.

PRIORITY

This application claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Patent Application Ser. No. 62/583,260 filed on Nov. 8,2017, the entire contents of which are incorporated herein by reference.

FIELD

The present disclosure relates generally to a communication system, andmore particularly, to a filter/mixer structure for orthogonal frequencydivision multiplexing (OFDM) signal separation and inter carrierinterference (ICI) reduction.

BACKGROUND

OFDM is a modulation format that is used in many of the latest wirelessand telecommunications standards. One example of the use of OFDM is “5G”cellular. Next generation or “5G” telecommunications technologyrepresents a giant leap forward in both requirements and resources overthe current Long Term Evolution (LTE) telecommunications technology.Under the 3^(rd) Generation Partnership Project (3GPP), the “New RadioAccess Technology,” often called “NR” (new radio), is being developed asthe underlying physical layer technology enabling 5G. See, e.g., Zaidiet al., Waveform and Numerology to Support 5G Services and Requirements,IEEE Communications Magazine (November 2016), pages 90-98; and 3GPP TSGRAN WG1 Mtg #86 Tdoc R1-168526 (Sep. 2, 2016), draft 3GPP TR 38.802,Study of New Radio (NR) Access Technology—Physical Layer Aspects, whichare both incorporated herein by reference in their entirety.

In terms of resources, it is expected that 5G may have access tofrequency bands from under 6 GHz (where the current LTE frequency bandsare) up to 100 GHz. In terms of requirements, three 5G categories areoften discussed:

-   -   enhanced mobile broadband (eMBB), requiring very high data rates        and large bandwidths;    -   Ultra-reliable low latency communications (URLLC), requiring        very low latency, and very high reliability and availability;        and    -   Massive machine type communications (mMTC), requiring low        bandwidth, high connectivity, enhanced coverage, and low energy        consumption on the user end.

One aspect of the 5G technologies is the changes to the physical layer,in which, as mentioned above, is often referred to as NR by the 3GPP.Numerology (i.e., subcarrier spacing (SCS) and waveform parameters, suchas the cyclic prefix (CP)) is presently a non-issue because, in LTE,there is only one numerology in which, for example, the SCS is always 15kHz. In a radio environment such as the current LTE environment, it is arelatively simple task for a user equipment (UE) to roughly synchronizewith the signal and, based on their preset mapping in the frequencydomain, find the primary synchronization signals (PSSs) and secondarysynchronization signals (SSSs) in the time domain to fully synchronize.

By contrast, because of the range of 5G requirements, NR must havemultiple numerologies in order to encompass the range of simultaneoususage (from relatively low bandwidth, like mMTC, to extremely highbandwidth, like 4K video on eMBB). In practice, this means, for example,there may be multiple SCSs, such as, for example, 15 kHz, 30 kHz, and 60kHz, of different numerologies transmitting at the same time and on atleast partially overlapping frequency bands.

Thus, a UE in 5G NR must be able to determine, isolate, and synchronizeto more than one numerology—a new requirement for the UE.

Similar issues may arise in other communication systems where OFDMsignal may be located near OFDM signals with different numerology,non-OFDM signals or OFDM signals that have the same numerology but havefrequency offset of fraction of subcarrier or symbol position timeoffset.

All of the situations described above will give rise to intercarrierinterference (ICI) into the OFDM signal.

SUMMARY

Accordingly, the present disclosure has been made to address at leastthe problems and/or disadvantages described herein and to provide atleast the advantages described below.

According to an aspect of the present disclosure, a method is provided,including performing a first mixing on an input signal which frequencyrotates the input signal such that one end of a target signal in theinput signal is within one end of a passband of a first filter and asecond filter in the frequency domain; performing, by the first filter,a first filtering on the first mixed input signal; performing a secondmixing on the first filtered input signal which frequency rotates thefirst filtered input signal such that the opposite end of the targetbandwidth in the frequency domain is within the opposite end of thepassband; performing, by the second filter, a second filtering on thesecond mixed input signal; and performing a third mixing on the secondfiltered input signal which frequency rotates the second filtered inputsignal such that the target bandwidth returns to its original locationin the frequency domain in the input signal.

According to an aspect of the present disclosure, a method forconstructing a variable-bandwidth digital filter capable of separatingone of a plurality of possible target bandwidths from a received signalis provided, including constructing a three mixer, two filter (3M2F)structure that includes a first mixer, which frequency rotates an inputsignal such that one end of a target bandwidth in the input signal iswithin one end of a passband of a first filter and a second filter inthe frequency domain; the first filter which filters an output of thefirst mixer; a second mixer which frequency rotates an output of thefirst filter such that the opposite end of the target bandwidth in thefrequency domain is within the opposite end of the passband; the secondfilter that filters an output of the second mixer; and a third mixerwhich frequency rotates an output of the second filter such that thetarget bandwidth returns to its original location in the frequencydomain in the input signal. When only a single set of filtercoefficients are used for both the first filter and the second filter,both the first filter and the second filter may comprise identicalfixed-bandwidth filters.

According to an aspect of the present disclosure, a variable-bandwidthdigital filter capable of isolating each of a plurality of receivablenumerologies in a mixed numerology environment is provided, including athree mixer, two filter (3M2F) structure, that includes a first mixerwhich frequency rotates an input signal such that one end of a targetnumerology in the input signal is within one end of a passband of afirst filter and a second filter in the frequency domain; the firstfilter which filters an output of the first mixer; a second mixer whichfrequency rotates an output of the first filter such that the oppositeend of the target bandwidth in the frequency domain is within theopposite end of the passband; the second filter which filters an outputof the second mixer; and a third mixer which frequency rotates an outputof the second filter such that the target numerology returns to itsoriginal location in the input signal in the frequency domain. When onlya single set of filter coefficients are used for both the first filterand the second filter, both the first filter and the second filter maycomprise identical fixed-bandwidth filters.

According to an aspect of the present disclosure, an apparatus isprovided, including one or more non-transitory computer-readable media;and at least one processor which, when executing instructions stored onone or more non-transitory computer readable media, performs the stepsof performing a first mixing on an input signal which frequency rotatesthe input signal such that one end of a target bandwidth in the inputsignal is within one end of a passband of a first filter and a secondfilter in the frequency domain; performing, by the first filter, a firstfiltering on the first mixed input signal; performing a second mixing onthe first filtered input signal which frequency rotates the firstfiltered input signal such that the opposite end of the target bandwidthin the frequency domain is within the opposite end of the passband;performing, by the second filter, a second filtering on the second mixedinput signal; and performing a third mixing on the second filtered inputsignal which frequency rotates the second filtered input signal suchthat the target bandwidth returns to its original location in thefrequency domain in the input signal.

According to an aspect of the present disclosure, a method ofmanufacturing a chipset, which includes at least one processor which,when executing instructions stored on one or more non-transitorycomputer readable media, performs the steps of performing a first mixingon an input signal which frequency rotates the input signal such thatone end of a target bandwidth in the input signal is within one end of apassband of a first filter and a second filter in the frequency domain;performing, by the first filter, a first filtering on the first mixedinput signal; performing a second mixing on the first filtered inputsignal which frequency rotates the first filtered input signal such thatthe opposite end of the target bandwidth in the frequency domain iswithin the opposite end of the passband; performing, by the secondfilter, a second filtering on the second mixed input signal; andperforming a third mixing on the second filtered input signal whichfrequency rotates the second filtered input signal such that the targetbandwidth returns to its original location in the frequency domain inthe input signal; and the one or more non-transitory computer-readablemedia which store the instructions.

According to an aspect of the present disclosure, a method of testing anapparatus is provided, including testing whether the apparatus has atleast one processor which, when executing instructions stored on one ormore non-transitory computer readable media, performs the steps ofperforming a first mixing on an input signal which frequency rotates theinput signal such that one end of a target bandwidth in the input signalis within one end of a passband of a first filter and a second filter inthe frequency domain; performing, by the first filter, a first filteringon the first mixed input signal; performing a second mixing on the firstfiltered input signal which frequency rotates the first filtered inputsignal such that the opposite end of the target bandwidth in thefrequency domain is within the opposite end of the passband; performing,by the second filter, a second filtering on the second mixed inputsignal; and performing a third mixing on the second filtered inputsignal which frequency rotates the second filtered input signal suchthat the target bandwidth returns to its original location in thefrequency domain in the input signal; and testing whether the apparatushas the one or more non-transitory computer-readable media which storethe instructions.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing detailed description, taken in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates an exemplary graph of frequency vs. time for twodifferent numerologies, to which a structure according to an embodimentof the present disclosure may be applied;

FIG. 2 illustrates an exemplary flowchart of a method for separating outa certain numerology from a mixed numerology signal, according to anembodiment of the present disclosure;

FIG. 3 illustrates an exemplary block diagram of a three mixer, twofilter (3M2F) structure for separating out a certain numerology from amixed numerology signal, according to an embodiment of the presentdisclosure;

FIG. 4 illustrates exemplary graphs of a signal as it is processed bythe 3M2F structure shown in FIG. 3, according to an embodiment of thepresent disclosure;

FIG. 5A illustrates a graph for signals using a first set of filtercoefficients in a 3M2F structure according to an embodiment of thepresent disclosure;

FIG. 5B illustrates a graph for signals using a second set of filtercoefficients in a 3M2F structure according to the embodiment of thepresent disclosure of FIG. 4;

FIG. 6 illustrates an exemplary flowchart of a method for implementing avariable-bandwidth digital filter for mixed numerologies using a 3M2Fstructure according to an embodiment of the present disclosure.

FIG. 7 illustrates an exemplary diagram of the present apparatus,according to an embodiment of the present disclosure; and

FIG. 8 illustrates an exemplary flowchart for manufacturing and testingthe present apparatus, according to an embodiment of the presentdisclosure.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure are described indetail with reference to the accompanying drawings. It should be notedthat the same elements are designated by the same reference numeralsalthough they are shown in different drawings. In the followingdescription, specific details such as detailed configurations andcomponents are merely provided to assist in the overall understanding ofthe embodiments of the present disclosure. Therefore, it should beapparent to those skilled in the art that various changes andmodifications of the embodiments described herein may be made withoutdeparting from the scope of the present disclosure. In addition,descriptions of well-known functions and constructions are omitted forclarity and conciseness. The terms described below are terms defined inconsideration of the functions in the present disclosure, and may bedifferent according to users, intentions of the users, or custom.Therefore, the definitions of the terms should be determined based onthe contents throughout the specification.

The present disclosure may have various modifications and variousembodiments, among which embodiments are described below in detail withreference to the accompanying drawings. However, it should be understoodthat the present disclosure is not limited to the embodiments, butincludes all modifications, equivalents, and alternatives within thescope of the present disclosure.

Although terms including an ordinal number such as first and second maybe used for describing various elements, the structural elements are notrestricted by the terms. The terms are only used to distinguish oneelement from another element. For example, without departing from thescope of the present disclosure, a first structural element may bereferred to as a second structural element. Similarly, the secondstructural element may also be referred to as the first structuralelement. As used herein, the term “and/or” includes any and allcombinations of one or more associated items.

The terms herein are merely used to describe various embodiments of thepresent disclosure but are not intended to limit the present disclosure.Singular forms are intended to include plural forms unless the contextclearly indicates otherwise. In the present disclosure, it should beunderstood that the terms “include” or “have” indicate existence of afeature, a number, a step, an operation, a structural element, parts, ora combination thereof, and do not exclude the existence or probabilityof addition of one or more other features, numerals, steps, operations,structural elements, parts, or combinations thereof.

Unless defined differently, all terms used herein have the same meaningsas those understood by a person skilled in the art to which the presentdisclosure belongs. Terms such as those defined in a generally useddictionary are to be interpreted to have the same meanings as thecontextual meanings in the relevant field of art, and are not to beinterpreted to have ideal or excessively formal meanings unless clearlydefined in the present disclosure.

Various embodiments may include one or more elements. An element mayinclude any structure arranged to perform certain operations. Althoughan embodiment may be described with a limited number of elements in acertain arrangement by way of example, the embodiment may include moreor less elements in alternate arrangements as desired for a givenimplementation. It is worthy to note that any reference to “oneembodiment” or “an embodiment” means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment. The appearance of the phrase“one embodiment” (or “an embodiment”) in various places in thisspecification does not necessarily refer to the same embodiment.

Embodiments of the present disclosure provide systems, methods, andapparatuses for filtering out one of a plurality of possiblenumerologies in a mixed numerology environment. Hereinafter,“numerology” may be used to signify a numerology as well as a signal ofa certain numerology, as the term is commonly used among those ofordinary skill in the art. In one aspect, a variable bandwidth digitalfilter uses two fixed bandwidth filters and three mixers.

As mentioned above, the NR standard is currently being developed, so thechannel structure for NR is not finalized yet. In the current draft 3GPPTR 38.802 (Study of New Radio (NR) Access Technology—Physical Layer,ver. 14.2.0 (2017 September), which is incorporated herein in itsentirety), a UE has one reference numerology of 15 kHz in a given NRcarrier which defines subframe duration for the given NR carrier, i.e.,a subframe duration fixed to 1 ms. For a reference numerology withSCS=15 kHz, each remaining numerology has an SCS=2^(m)×15 kHz, where mis an integer, the subframe duration is exactly ½^(m) ms.

Although embodiments of the present disclosure are described withreference to the NR standard, the present disclosure is not limitedthereto, and embodiments of the present disclosure may be implemented inany communication environment where one OFDM signal co-exists withanother OFDM signal that has different SCS, frequency, or time offset,or a non-OFDM signal with small frequency separation between the twosignals.

More generally, the filter/mixer structure described herein may helpseparate out signals and mitigate interference in a wide variety ofcircumstances and particularly in a system using orthogonal frequencydivision multiplexing (OFDM) where sampling using the fast Fouriertransform (FFT) is used to recover OFDM symbols in the receiver. Whilethe present disclosure discusses embodiments using OFDM symbols, thepresent disclosure is not limited thereto, but includes non-OFDM signalsas well. The interference mitigated by embodiments of the presentdisclosure may be inter carrier interference (ICI) caused by frequencyoffsets and/or varying symbol lengths (such as in a mixed numerologyenvironment), or other causes. For example, in a situation where twoorthogonal frequency division multiplexed (OFDM) signals are receivedwith identical small SCS and frequency offsets, an embodiment of thepresent disclosure could isolate one signal while reducing oreliminating ICI. Moreover, the present disclosure may be applied tohybrid OFDM/non-OFDM signals as well as non-OFDM signals.

FIG. 1 illustrates an exemplary graph of frequency vs. time for twodifferent numerologies, to which a filter structure according to anembodiment of the present disclosure may be applied.

In FIG. 1, reference numeral 110 indicates a signal with a numerologyhaving an SCS=15 kHz and reference numeral 120 indicates a signal with anumerology having an SCS=60 kHz. For the numerology 110 with SCS=15 kHz,each OFDM signal has a time duration four (4) times each OFDM signal forthe numerology 120 with SCS=60 kHz. For the numerology 120 with SCS=60kHz, each subcarrier has a frequency band four (4) times the size ofeach subcarrier for the numerology 110 with SCS=15 kHz. This is inaccordance with the relationship above where the reference numerologyhas an SCS=15 kHz and the other numerology has m=2, so that SCS=2^(m)×15kHz=60 kHz and the subframe duration is ½² ms=¼ ms.

As discussed above, in current LTE applications, only one numerology isallowed, the subcarrier spacing is a constant (i.e., SCS=15 kHz), andthe symbol duration is also a constant (an inverse of the SCS). Thisresults in the OFDM symbols of different subcarriers maintainingorthogonality, and thus they may be decoded without experiencinginter-carrier interference (ICI).

By contrast, in 5G NR, the spectrum within a channel is partitionedbetween OFDM components with different SCSs and symbol durations—i.e.,different numerologies. When there are transmissions with multiplenumerologies, orthogonality between subcarriers of differentnumerologies may not be maintained. Thus, for example, when decoding thesignal 110 with the numerology having SCS=15 kHz, there may be ICI fromthe signal 120 with the numerology having SCS=60 kHz, and vice versa.When subcarriers of different numerologies are placed with a smallfrequency separation between them, there will be spectral leakagebetween the subcarriers with different numerologies, resulting in anincrease in measured error vector magnitude (EVM) and in an increase inbit error rate.

Typically, to reduce ICI while separating out one numerology frommultiple possible received numerologies in a received signal, twotechniques are used: windowing and filtering. In the former, a windowmeeting the Nyquist criteria is used to isolate the signal having thedesired numerology from the received mixed numerology signal. As wouldbe known to one of ordinary skill in the art, windows which could beused include the Hanning window, the triangular window, and many more.

When using filtering, a finite impulse response (FIR) or an infiniteimpulse response (IIR) filter centered on the portion of a receivedsignal allocated to the desired numerology can be used. Whether thefilter should be real or complex depends on whether the desirednumerology is symmetric around the center of the baseband spectrum inputto the filter. A mixed numerology system such as being considered andset under 3GPP may have variable bandwidth allocation inside a channeland the desired signal numerology inside a channel may also vary, undercontrol of the base station, i.e., an enhanced NodeB (eNB) or an NR(next generation) NB (gNB).

Accordingly, in a mixed numerology system such as 5G NR, a large numberof filters (and/or the storage of a large number of sets of filtercoefficients) would be required to support all of the bandwidthallocations possible under the different numerologies. The differentpositions of the target numerology centers may be handled by digitaldown-conversion of the numerology's center to the center of the inputspectrum prior to the application of filtering. However, each possiblebandwidth allocation would require its own set of filter coefficients tobe used in the filter, resulting in the storage requirements of a largenumber of sets of filter coefficients (one for each bandwidth supported)for one or more programmable filters, the resource requirements of alarge number of fixed filters, or the requirements of a mixture of thetwo (i.e., both fixed and programmable filters). All of these resourcerequirements would necessarily have ripple effects as well. For example,a programmable filter would need to be reconfigured with a new set ofcoefficients when the desired received numerology has changed, requiringthe download of the new set of coefficients from memory and loading ofthe new set of coefficients into the programmable filter, therebyslowing down the entire process.

As briefly mentioned above, in embodiments according to the presentdisclosure, the filtering necessary for mixed numerologies is performedusing only a small number of sets of filter coefficients (and only asingle set of filter coefficients in an embodiment discussed below),which may be hard-wired (particularly when only one set is needed) orselected via a multiplexer. When only a single set of filtercoefficients is used, as with an embodiment of the present disclosurediscussed below, there is no need for multiplexing of coefficients norany need for storage of multiple sets of coefficients.

According to an embodiment of the present disclosure, a filter/mixerstructure, which may be referred to herein as thethree-mixers-two-filters (3M2F) structure, requires storage of only asingle set of filter coefficients to be used by both filters in mostpractical instances. The passband provided by the single set of filtercoefficients is greater than or equal to the widest possible bandwidththat may be occupied by a single numerology. However, as discussedfurther below, when the smallest of the possible receivable numerologiesis less than a certain minimum bandwidth, different sets of filtercoefficients may be required, however the total number of sets ofcoefficients remains small.

FIG. 2 illustrates an exemplary flowchart of a method for separating outa certain numerology from a mixed numerology signal, according to anembodiment of the present disclosure. This embodiment assumes a 3M2Ffilter/mixer structure where the two filters use the same set of filtercoefficients, and the input signal spectrum (“INPUT”) is assumed to havebeen sampled such that its center equals f_(s), the sampling frequency,and spans, at the most, from −f_(s)/2 to +f_(s)/2. The INPUT signal hasboth the desired numerology and other undesired numerologies.

At 210 of FIG. 2, the first mixing is performed. The first mixerfrequency rotates (or “moves” in the frequency domain) the input signalspectrum INPUT so that when the first filter is applied to the outputsignal of the first mixer, the lowest frequency subcarrier of thedesired numerology coincides with the lower frequency passband boundaryof the first filter. At 220 of FIG. 2, the first filtering is performed.Because every numerology fits within the filter passband (since thepassband provided by both the first and second filter is greater than orequal to the widest possible bandwidth that may be occupied by a singlenumerology), after the first filter is applied, the signal remainingwill constitute the desired numerology and whatever is passed throughthe passband from the lower frequency passband boundary up to the higherfrequency passband boundary. Although the first mixing and firstfiltering is described at 210-220 in FIG. 2 in relation to the lowestfrequency subcarrier of the numerology and the lower frequency boundaryof the filter passband, this is arbitrary, and the first mixing andfirst filtering may be performed in relation to the highest frequencysubcarrier of the numerology and the higher frequency boundary of thefilter passband, as will be described in reference to 230-240 of FIG. 2.

At 230 of FIG. 2, the second mixing is performed. The second mixer movesthe signal output by the first filter so that when the second filter isapplied, the highest frequency subcarrier of the desired numerologycoincides with the higher frequency passband boundary of the secondfilter. At 240 of FIG. 2, the second filtering is performed. Continuingwith the same example, if the first filter cut off any of the inputsignal located below the lowest frequency subcarrier of the desirednumerology, the second filter cuts off any of the signal spectrum abovethe highest frequency subcarrier of the desired numerology. Once thesecond filter is applied, the signal remaining will constitute only thedesired numerology. However, because of the movement in the frequencydomain caused by the mixers, the desired numerology after the secondfilter is not located at its original location in the input spectrum.Accordingly, at 250 of FIG. 2, the third mixer moves the desirednumerology output by the second filter back to its original location inthe input spectrum INPUT, thereby outputting an output signal (“OUTPUT”)consisting of just the desired numerology.

Using methods and apparatuses according to embodiments of the presentdisclosure, a receiver may separate a certain numerology from a receivedsignal containing many possible numerologies, one or more of which havedifferent SCSs and symbol durations. The embodiment described inrelation to FIG. 2 is simplified for ease of explanation; however, asdiscussed below and as would be understood by one of ordinary skill inthe art, one or more of the filters or mixers may perform additionaltasks, more than one set of filter coefficients may be used, the fixedfilters in FIG. 2 may be programmable digital filters, etc., and stillremain within the scope of the present disclosure.

In a 5G NR receiver, subcarriers may be transmitted with a +½ subcarrieroffset to prevent direct current (DC) or 0 Hz offsets of the transmitterand the receiver from damaging DC subcarriers of the OFDM signal. The +½subcarrier offset must be removed at the receiver. The third mixer cancombine its function of restoring the original location of the targetnumerology with the removal of +½ subcarrier frequency offset.

As previously mentioned, the above procedure can be applied when thedesired numerology bandwidth is greater than a certain minimum amountwhich depends upon the passband of the filters. For target numerologybandwidths smaller than this minimum, some subcarriers will survive theoperation described above. Under such circumstances, 3M2F operation mustbe performed with a different set of coefficients, where the identicalfilters in the 3M2F structure are modified by using a different set offilter coefficients to form a narrower passband. In most practicalapplications, a second set of coefficients is unnecessary, since anysurviving subcarriers are located a large distance away from the targetnumerology and produce only a small amount of ICI.

FIG. 3 illustrates an exemplary block diagram of a filter/mixerstructure according to an embodiment of the present disclosure. FIG. 4illustrates exemplary graphs of a signal as it is processed by thefilter/mixer structure shown in FIG. 3, according to an embodiment ofthe present disclosure. Some of the reference numerals of FIG. 4 alsoappear in FIG. 3, indicating where the signal of thegraph/representation indicated by the reference numeral in FIG. 4 wouldbe located in the 3M2F filter/mixer structure of FIG. 3.

In FIG. 3, a 3M2F filter/mixer structure according to an embodiment ofthe present disclosure is shown, having mixers MXR1 310, MXR2 320, andMXR3 330, filters FLTR1 315 and FLTR2 325, numerically controlledoscillators (NCOs) NCO₁ 311, NCO₂ 321, and NCO₃ 331, generating thefrequencies for mixers MXR1 310, MXR2 320, and MXR3 330, respectively,and frequency control registers Freq. Control 1 313, Freq. Control 2323, and Freq. Control 3 333, supplying the frequency control words(FCWs) to NCO₁ 311, NCO₂ 321, and NCO₃ 331, respectively. The frequencycontrol registers may be implemented in a wide variety of ways, as wouldbe understood by one of ordinary skill in the art. For example, the FCWsmay be selected from one or more lookup tables (LUTs) and input to oneor more of the frequency control registers by a controller.

The 3M2F mixer/filter structure in FIG. 3 may be implemented as, forexample, an integrated circuit (IC) or part of an IC.

In FIGS. 3 and 4, the input signal/initial spectrum 401 (as well as theoutput signal 430) is a two-sided complex signal (i.e., both signals are“I+jQ” in FIG. 3). The sampling frequency, which is applied to the inputsignal before being input, is represented by f_(s), the bandwidth ofeach of the filters FLTR1 315 and FLTR2 325 is represented by BW 417 and427, respectively (and would be BW/2 in a one-sided signal), and thebandwidth of the target numerology is represented by BW_(target) 405,which lies between f_(L) and f_(H), as shown in FIG. 4. Because f_(s)was the sampling rate, the frequency graphs in FIG. 4 run from −f_(s)/2to +f_(s)/2, with the zero point in the center. Based on thisdescription, Equations (1)(a) and (1)(b) below would hold true:

$\begin{matrix}{{f_{H} - f_{L}} \leq {BW}} & {(1)(a)} \\{{- \frac{f_{s}}{2}} \leq f_{L} < f_{H} \leq {+ \frac{f_{s}}{2}}} & {(1)(b)}\end{matrix}$

Based on these assumptions, the frequency control words for NCO₁ 311,NCO₂ 321, and NCO₃ 331 must generate the frequencies for mixers MXR1310, MXR2 320, and MXR3 330, respectively, as shown in Table 1:

TABLE 1 Frequencies generated by the NCOs for the Mixers Frequency ofNCO generated based on input Frequency Control Word (FCW) Comments FCW →−f_(L) − BW/2 Since f_(L) is on the negative side NCO₁ 311 → of theinput signal/initial MXR1 310 spectrum 401 in FIG. 4, the result of thisequation is a positive value, resulting in MXR1 310 moving the inputsignal/initial spectrum 401 to the right (i.e., in the positivedirection) at 410. FCW → −f_(H) + BW/2 − Since f_(L) is on the negativeside NCO₂ 321→ (−f_(L) − BW/2) and f_(H) is on the positive side of MXR2320 or the input signal/initial spectrum BW + f_(L) − f_(H) 401, thisequation becomes or BW − BW_(target), resulting in BW − (f_(H) − f_(L))MXR2 320 moving signal 415 to the right (i.e., in the positivedirection) at 420. FCW → f_(H) − BW/2 This equation/frequency moves NCO₃331→ signal 425 back to its original MXR3 330 location in inputsignal/initial spectrum 401, as shown at 430. When necessary, −½subcarrier spacing adjustment can be added here.

As indicated in the Comments of Table 1, and mentioned further above,the third mixer (MXR3 330 in the embodiment shown in FIG. 3) can combineits function of restoring the original location of the target numerologywith the removal of +½ subcarrier frequency offset. Specifically, thismay be done by, for example, changing the Frequency control 3 registerby an amount corresponding to frequency change of ½ SCS. In addition,NCO₃ phase control must be periodically reset to a proper value at thebeginning of each OFDM symbol.

In FIG. 4, the input signal/initial spectrum 401 (“Initial Spectrum”) isshown having both the target numerology BW_(target) 405 (“TargetNumerology”), lying between f_(L) and f_(H), and other undesirablesignals, such as non-target numerologies. Moreover, the targetnumerology BW_(target) 405 is not properly located within the inputspectrum for the first filter FLTR1 315 to remove unwanted signals belowthe lowest frequency subcarrier of the target numerology. Accordingly,the input signal/initial spectrum 401 is input into MXR1 310 in FIG. 3,which moves the target numerology, as shown at 410 in FIG. 4, so thatthe lowest frequency subcarrier of the target numerology coincides withthe lower frequency boundary 417-L of the filter passband 417.

The signal output by MXR1 310 at 410 is input into FLTR1 315, which hasfrequency passband BW 417, demarcated by lower frequency passband 417-Land higher frequency passband boundary 417-H, shown in FIG. 4. In thisembodiment, FLTR1 315 is intended to remove everything in the inputsignal lower in frequency than the lowest frequency subcarrier in thetarget numerology by filtering out frequencies below lower frequencypassband boundary 417-L. The frequency passband BW 417 of FLTR1 315 mayalso remove a portion of unwanted signal above the higher frequencypassband boundary 417-H, but will not necessarily eliminate all of theunwanted signal above the highest frequency subcarrier of the targetnumerology, in which case the remaining undesirable signal must then beremoved by the next mixer/filter stage in this 3M2F embodiment.

As shown in FIG. 4, the signal output by FLTR1 315 at 415 may still havea band of undesirable signal above the highest frequency subcarrier ofthe target numerology. Thus, the overall signal will need to be movedagain so the next filter, FLTR2 325 having frequency passband BW 427which is identical to the frequency passband BW 417 of FLTR1 315, canremove the remaining undesirable signal. Accordingly, the signal at 415is input into MXR2 320 in FIG. 3, which moves the target numerology suchthat the highest frequency subcarrier of the target numerology coincideswith the higher frequency passband boundary 417-H and the undesirablesignal/noise lies outside the passband BW 427 of FLTR2 325, as shown at420 in FIG. 4. Next, the signal output by MXR2 320 at 420 is filtered byFLTR2 325, which results in frequencies above the higher passbandboundary of passband BW 427 being removed, as shown at 425 in FIG. 4. Inother words, FLTR2 325 is intended to remove everything in the inputsignal higher in frequency than the highest frequency subcarrier of thetarget numerology.

As mentioned above, the order of operation may be reversed—i.e., thefirst mixer/first filter may remove the unwanted higher frequencysignals and the second mixer/second filter could remove the unwantedlower frequency, as would be known to a person of ordinary skill in theart.

However, although the signal output by FLTR2 325 at 425 constitutes onlythe target numerology, the target numerology in the signal at 425 is notlocated at the right place in the spectrum—i.e., the target numerologyis not located between f_(L) and f_(H) as shown in input signal/initialspectrum 401 of FIG. 4. Accordingly, MXR3 330 moves the targetnumerology in signal output by FLTR2 325 at 425 back to its originallocation in the input spectrum, as shown by signal output by MXR3 330 at430 in FIG. 4.

Thus, according to the embodiment of the present disclosure shown inFIG. 3, a target numerology may be separated out from a signal receivedin a mixed numerology communication system/environment, as shown in FIG.4.

When implementing a mixer/filter structure according to embodiments ofthe present disclosure, the filter bandwidth BW must be selected toaccommodate all possible numerologies which may be received in the mixednumerology system. Depending on the circumstances of the particularimplementation, as would be understood by one of ordinary skill in theart, another set of coefficients and/or component(s) (such as, e.g., afilter or mixer) may be needed or may be simply moresuitable/appropriate. In an embodiment with more than one set of filtercoefficients, the filters in the 3M2F may be programmable rather thanfixed.

For example, as mentioned above, there is a certain minimum targetnumerology threshold below which the 3M2F filter/mixer structure in FIG.3 may need a different set of filter coefficients. It is unlikely,however, that more than one set of filter coefficients would ever berequired. In any event, if there are target numerologies below thiscertain minimum target numerology threshold, the first set of filtercoefficients would not be sufficient to remove all unwantedsignal/noise.

More specifically, Equation (2)(a) below represents the rejectedbandwidth BW_(rej) provided by one set of filter coefficients:BW _(rej) =f _(s) −BW _(3M2F)  (2)(a)where the filter bandwidth BW_(3M2F) must be greater than or equal tothe largest possible numerology signal, as represented by Equation(2)(b):BW _(3M2F)≥max(BW _(target))  (2)(b)and the certain minimum amount filter bandwidth BW_(min_target) isrepresented by Equation (2)(c):BW _(min_target) =f _(s)−2×BW _(rej)  (2)(c)

Accordingly, if the smallest possible numerology is greater than orequal to the minimum bandwidth BW_(min_target), i.e., the minimum targetnumerology threshold for the set of filter coefficients of the filters,only one set of coefficients is needed, and both filters may behard-wired (“fixed”) with that single set of coefficients. However, ifthere are one or more possible numerologies less than minimum bandwidthBW_(min_target), i.e., the minimum target numerology threshold for theset of filter coefficients, one or more additional sets of filtercoefficients may be needed because otherwise undesired signal willremain. As stated above, in most practical cases, only a single set offilter coefficients would typically be required. Table 2 summarizesthese two possibilities (i.e., one set of filter coefficients or morethan one set of filter coefficients):

TABLE 2 CONDITION REQUIREMENTS/RESULTS min(BW_(target)) ≥ BW_(min) _(—)_(target) Only single set of coefficients required. or, equivalently Alltarget numerologies greater than or all possible BW_(target) ≥ f_(s) −equal to the minimum target numerol- 2 × BW_(rej) ogy threshold arecaptured by the single set of filter coefficients. All subcarriersoutside the desired numerology are attenuated. Some subcarriers aredouble-attenuated under strict inequality. min(BW_(target)) < BW_(min)_(—) _(target) Additional set(s) of coefficients may be or, equivalentlyrequired. at least one possible BW_(target) < At least one targetnumerology is lesser f_(s) − 2 × BW_(rej) than the minimum targetnumerology threshold for the first set of coefficients. Some subcarriersoutside desired numerology survive if first set of coefficients wereused. Surviving subcarriers are not immediately adjacent to the targetnumerology and may be ignored in most practical applications (i.e., forpractical purposes the single set of coefficients may still sufficeunder these conditions)

As indicated in Table 2, spectral leakage/surviving subcarriers may makeanother set of filter coefficients desirable in some implementations, aswould be understood by one of ordinary skill in the art. A specificexample is described in relation to FIGS. 5A and 5B below.

FIG. 5A illustrates a graph for signals processed in a 3M2F using afirst set of coefficients, where FIG. 5B illustrates a graph of signalsprocessed using a second set of filter coefficients, as needed,according to an embodiment of the present disclosure. In thisdescription, bandwidth is measured in number of subcarriers (sc),thereby making the description more universally applicable. Normally,when discussing NR systems, the number of subcarriers is quantized to aResource Block (RB) size, where RB=12 subcarriers. In the example, thefollowing conditions are assumed for the first set of filtercoefficients, corresponding to FIG. 5A:f _(s)=4096 subcarriers (sc)BW _(1st set)=max(BW _(target))=3300 scBW _(rej_1st set) =f _(s) −BW _(1st set)=4096−3300=796 scBW _(min_target_1st_set) =f _(s)−2×BW _(rej_1st set)=2504 sc

As shown above, for FIG. 5A, the sampling frequency f_(s) is 4096 sc;the filter bandwidth (for each filter in the 3M2F) BW_(1st_set) is 3300sc, which is equivalent to the largest possible numerology bandwidth,and max(BW_(target))=3300 sc. Thus, the minimum target bandwidth Thus,the minimum target bandwidth BW_(min_target) (i.e., the minimum targetnumerology threshold for the first set of filter coefficients)=2504 sc.In FIG. 5A, there are lines indicating the BW_(target) 510-A;BW_(target)+BW_(rejL)+BW_(rejR) 520-A, where BW_(rejL) is the rejectedbandwidth on the left side, BW_(rejR) is the rejected bandwidth on theright side, and BW_(rej/2)≈BW_(rejL)≈BW_(rejR) 530-A; the doubleattenuated/rejected bandwidth BW_(DoubleRej) 540-A; and the unrejectedbut attenuated bandwidth BW_(unrejSC) 550-A.

Because the minimum target bandwidth BW_(min_target_1st_set)=2504 sc(i.e., the minimum target numerology threshold) using the first set offilter coefficients, all target numerologies with a bandwidth greaterthan or equal to 2504 sc will be successfully captured and separated outand thus no further filtering may be required. However, some distantsubcarriers of adjacent numerologies, i.e., non-target numerologiespresent when target numerology a bandwidth less than the minimum targetnumerology threshold for the first set of filter coefficients (i.e.,2504 sc), may survive the filtering operation. In FIG. 5A, the regionfor these non-target numerology subcarriers is indicated by lineBW_(unrejSC) 550-A. Since these subcarriers are some distance away fromthe target numerology, the EVM contribution due to spectral leakageafter filtering with a 3M2F using the first set of filter coefficientswill not be very high.

However, under some conditions and in certain implementations, such asif further reduction in ICI is necessary for an application, a secondset of coefficients may be used, as shown in FIG. 5B. As anotherexample, if there are desired target numerologies with a bandwidth lessthan 2504 sc (i.e., if there are target numerologies less than theminimum target numerology threshold), a second set of filtercoefficients may be used.

If a second set of coefficients is desirable to, for example, separateout non-target numerologies with a bandwidth less than 2504 sc, thefollowing parameters may be used for the second set of filtercoefficients, as illustrated by FIG. 5B:f _(s)=4096 subcarriers (sc)BW _(2nd set)=max(BW _(target_2nd_stage)=)2504 scBW _(rej_2nd set) =f _(s) −BW _(2nd set)=4096−2504=1592 scBW _(min_target_2nd_set) =f _(s)−2×BW _(rej_2nd set)=912 sc

As shown above, for FIG. 5B, the sampling frequency f_(s) is 4096 sc,the filter bandwidth (for each filter in the 3M2F) BW_(2nd_set) is 2504sc, which was the minimum possible numerology bandwidthBW_(min_target_1st_set) set using the first set of filter coefficients(i.e., the minimum target numerology threshold for the first set offilter coefficients). The rejected bandwidth is broader than using thefirst set of filter coefficients, with BW_(rej_2nd_set)−1592 sc, and theminimum target bandwidth BW_(min_target_2nd_set) (i.e., the minimumtarget numerology threshold for the second set of filtercoefficients)=912 sc. Because these subcarriers are separated from anypossible target numerologies to be isolated by using the second set offilter coefficients by a wider rejection band (compared with the firstset), the second set will produce less spectral leakage. However, ifeven the second set of filter coefficients is not sufficient to reachthe desired tolerances for the particular scenario/implementation,another set, i.e., a third set of filter coefficients, may be employedin like manner to the second set of coefficients. Sets of coefficientsmay be added until the desired effect is achieved, although, as notedabove, one set will be sufficient in most cases, and two sets of filtercoefficients for most of the remaining cases.

The same lines as were shown in FIG. 5A are also shown in FIG. 5B. InFIG. 5B, there are lines indicating the BW_(target) 510-B;BW_(target)+BW_(rejL)+BW_(rejR) 520-B; BW_(rej)/2≈BW_(rejL)≈BW_(rejR)530-B; the double attenuated/rejected bandwidth BW_(DoubleRej) 540-B;and the unrejected but attenuated bandwidth BW_(unrejSC) 550-B.

FIG. 6 illustrates an exemplary flowchart of a method for implementing avariable-bandwidth 3M2F digital filter for mixed numerologies accordingto an embodiment of the present disclosure.

At 610, the 3M2F mixer/filter structure, including three mixers and twofilters, is implemented in the manner shown in FIG. 3. The two filtersshare the same coefficients and thus have the same passband. Thepassband of the filters (BW_(filter_passband)) must be greater than orequal to the determined largest possible numerology (max(BW_(target))).

At 615, it is determined whether the criteria for the variable-bandwidth3M2F digital filter is met, where the criteria depends on the particularscenario, implementation, communication scheme, environment, etc. Forexample, the criteria may be whether the minimum/smallest numerologywhich may be received (min(BW_(target))) is greater than or equal to theminimum possible numerology which can be clearly isolated by the set offilter coefficients used by the two filters (the minimum targetnumerology threshold or, equivalently, BW_(min_target_threshold))—i.e.,min(BW_(target))≥BW_(min_target_threshold)?. Other possible criteriainclude, but are not limited to, target tolerances for spectral leakage,ICI, etc., which may depend upon the specific intended scenario,implementation, communication scheme, environment, etc.

615 is optional, and, in cases where it is predetermined that a singleset of filter coefficients are sufficient, 615 is not performed, butrather, at 620, only a single set of filter coefficients are used, whichmeans the two identical filters in the 3M2F are fixed and can behard-wired. Similarly, if it is determined that the filter criteria aremet at 615, the two identical filters are fixed and can be hard-wired.

If it is determined that the filter criteria are not met at 615, it isdetermined whether a second set of filter coefficients should be used at630. As stated above, in most cases, a second set of coefficients is notrequired, in which case the method proceeds back to 620. However, it maybe determined at 630 that a second set of filter coefficients may beneeded or helpful. For instance, following the filter criteria examplegiven above, i.e., min(BW_(target))≥BW_(min_target_threshold), if theminimum/smallest numerology which may be received is less than theminimum possible numerology which can be clearly isolated using thecurrent set of filter coefficients(min(BW_(target))<BW_(min_target_threshold) or, equivalently, thesmallest numerology is less than the minimum target numerologythreshold), a second set of filter coefficients may be used in order forthe 3M2F to sufficiently capture the target numerology.

If it is determined to use a second set of filter coefficients at 630,more than one set of filter coefficients are used at 640, which meansthe two filters are still identical, but variable (i.e., using more thanone set of filter coefficients), which may be implemented by havingprogrammable filters, hard-wired filters (although much more complexthan the fixed filters, of course), or filters implemented by acombination of software and hardware. For instance, still following theexample above, if the smallest numerology is less than the minimumtarget numerology threshold for the first set of filter coefficients(min(BW_(target))<BW_(min_target_threshold)) at 615, the second set offilter coefficients may be generated at 640 using the followingprocedure. First, the minimum target numerology threshold for the firstset of filter coefficients (BW_(min_target_threshold_1st_set)) is usedas the maximum possible target numerology (max(BW_(target_2nd_set))) forgenerating the second set of filter coefficients. As a result, thepassband of each of the two identical filters in the 3M2F when using thesecond set of filter coefficients (BW_(filter_passband 2nd_set)) will begreater than or equal to the largest possible numerology for the secondset of filter coefficients (max(BW_(target_2nd_set)), which is also theBW_(min_target_threshold_1st_set).

As stated above, normally only one or possibly two sets of coefficientswould actually be needed, as shown in FIG. 6. However, the presentdisclosure is not limited thereto, and additional coefficient sets maybe generated/implemented until the criteria of the specificvariable-bandwidth digital filter is met, which, in FIG. 6, wouldrequire a loop always returning to 615 after thegeneration/implementation of each new set of filter coefficients.

As shown and demonstrated by the embodiments described above, oneadvantage of embodiments according to the present disclosure is thereduced complexity and cost. Instead of storing a large number (possiblyhundreds) of sets of filter coefficients, in most practical instances,only one set is required for the two identical filters in the 3M2Fstructure. Furthermore, those coefficients can be hard-wired, instead ofbeing made programmable, which further reduces the complexity ofimplementation of multiplexers. In such a fixed/hard-wired identicalfilter 3M2F variable-bandwidth digital filter embodiment, theconstruction would be fairly straightforward and all of the componentswould be relatively inexpensive.

As shown and demonstrated by the embodiments described above, oneadvantage of embodiments according to the present disclosure is thereduction of inter-carrier interference (ICI). A UE which separates outa signal having a certain numerology from a received signal according toan embodiment of the present disclosure also reduces ICI, which isparticularly useful when in a communication system where ICI is presentbetween closely placed channels/frequencies.

As shown and demonstrated by the embodiments described above, oneadvantage of embodiments according to the present disclosure is toprovide a 3M2F variable-bandwidth digital filter which may be used tocapture both the largest and smallest numerologies possible in a mixednumerologies communication system. Another advantage of embodimentsaccording to the present disclosure is to provide a 3M2Fvariable-bandwidth digital filter which may be used to reduce ICIbetween closely placed channels/frequencies in a communication system.

Although embodiments of the present disclosure are described above withreference to the NR standard and mixed numerology communicationenvironments, the present disclosure is not limited thereto, andembodiments of the present disclosure may be implemented in anycommunication environment where there is small SCS and/or frequencyoffset.

More generally, the filter/mixer structure described herein may helpseparate out signals and mitigate interference in a wide variety ofcircumstances. Specifically, a 3M2F structure according to an embodimentof the present disclosure may be used to recover OFDM symbols from anFFT sampling of a received signal. While the present disclosurediscusses embodiments using OFDM symbols, the present disclosure is notlimited thereto, but includes non-OFDM signals as well. The interferencemitigated by embodiments of the present disclosure may be inter carrierinterference (ICI) caused by frequency offsets and/or varying symbollengths (such as in a mixed numerology environment), or otherimpediments. For example, in a situation where two orthogonal frequencydivision multiplexed (OFDM) signals are received with identical SCS andsmall frequency offsets, an embodiment of the present disclosure couldisolate one signal while also eliminating ICI. Moreover, the presentdisclosure may be applied to hybrid OFDM/non-OFDM signals as well asnon-OFDM signals.

FIG. 7 illustrates an exemplary diagram of the present apparatus,according to one embodiment. An apparatus 700 includes at least oneprocessor 710 and one or more non-transitory computer readable media720. The at least one processor 710, when executing instructions storedon the one or more non-transitory computer readable media 720, performsthe steps of performing a first mixing on an input signal whichfrequency rotates the input signal such that one end of a targetnumerology in the input signal is within one end of a passband of afirst filter and a second filter in the frequency domain; performing, bythe first filter, a first filtering on the first mixed input signalwhich attenuates any signal past the one end of the passband; performinga second mixing on the first filtered input signal which frequencyrotates the first filtered input signal such that the opposite end ofthe target numerology in the frequency domain is within the opposite endof the passband; performing, by the second filter, a second filtering onthe second mixed input signal which attenuates any signal past theopposite end of the passband; and performing a third mixing on thesecond filtered input signal which frequency rotates the second filteredinput signal such that the target numerology returns to its originallocation in the frequency domain in the input signal. Moreover, the oneor more non-transitory computer-readable media 720 stores instructionsfor the at least one processor 710 to perform those steps.

FIG. 8 illustrates an exemplary flowchart for manufacturing and testingthe present apparatus, according to one embodiment.

At 850, the apparatus (for example, a chipset) is manufactured,including at least one processor and one or more non-transitorycomputer-readable media. When executing instructions stored on the oneor more non-transitory computer readable media, the at least oneprocessor performs the steps of performing a first mixing on an inputsignal which frequency rotates the input signal such that one end of atarget bandwidth/numerology in the input signal is within one end of apassband of a first filter and a second filter in the frequency domain;performing, by the first filter, a first filtering on the first mixedinput signal which attenuates any signal past the one end of thepassband; performing a second mixing on the first filtered input signalwhich frequency rotates the first filtered input signal such that theopposite end of the target bandwidth/numerology in the frequency domainis within the opposite end of the passband; performing, by the secondfilter, a second filtering on the second mixed input signal whichattenuates any signal past the opposite end of the passband; andperforming a third mixing on the second filtered input signal whichfrequency rotates the second filtered input signal such that the targetbandwidth/numerology returns to its original location in the frequencydomain in the input signal. The one or more non-transitorycomputer-readable media store instructions for the at least oneprocessor to perform those steps.

At 860, the apparatus (in this instance, a chipset) is tested. Testing860 includes testing whether the apparatus has at least one processorwhich, when executing instructions stored on one or more non-transitorycomputer readable media, performs the steps of performing a first mixingon an input signal which frequency rotates the input signal such thatone end of a target bandwidth in the input signal is within one end of apassband of a first filter and a second filter in the frequency domain;performing, by the first filter, a first filtering on the first mixedinput signal which attenuates any signal past the one end of thepassband; performing a second mixing on the first filtered input signalwhich frequency rotates the first filtered input signal such that theopposite end of the target bandwidth in the frequency domain is withinthe opposite end of the passband; performing, by the second filter, asecond filtering on the second mixed input signal which attenuates anysignal past the opposite end of the passband; and performing a thirdmixing on the second filtered input signal which frequency rotates thesecond filtered input signal such that the target bandwidth returns toits original location in the frequency domain in the input signal; andtesting whether the apparatus has the one or more non-transitorycomputer-readable media which store instructions for the at least oneprocessor to perform the above steps.

In another embodiment, a 3M2F structure capable of isolating each of aplurality of receivable numerologies in a mixed numerology environmentis manufactured, where the 3M2F structure includes: a first mixer whichfrequency rotates an input signal such that one end of a targetnumerology in the input signal is within one end of a passband of afirst filter and a second filter in the frequency domain; the firstfilter which filters an output of the first mixer to attenuate anysignal past the one end of the passband; a second mixer which frequencyrotates an output of the first filter such that the opposite end of thetarget bandwidth in the frequency domain is within the opposite end ofthe passband; the second filter which filters an output of the secondmixer to attenuate any signal past the opposite end of the passband; anda third mixer which frequency rotates an output of the second filtersuch that the target numerology returns to its original location in theinput signal in the frequency domain. When only a single set of filtercoefficients are used for both the first filter and the second filter,both the first filter and the second filter may comprise identicalfixed-bandwidth filters. When more than one set of filter coefficientsare used for both the first filter and the second filter, both the firstfilter and the second filter may comprise identical programmablefilters, hard-wired filters, or a combination of hardware and software.

In this embodiment, an apparatus may be tested to determine whether itis a 3M2F structure capable of isolating each of a plurality ofreceivable numerologies in a mixed numerology environment according toembodiments of the present disclosure, by testing whether the apparatusincludes a first mixer which frequency rotates an input signal such thatone end of a target numerology in the input signal is within one end ofa passband of a first filter and a second filter in the frequencydomain; the first filter which filters an output of the first mixer toattenuate any signal past the one end of the passband; a second mixerwhich frequency rotates an output of the first filter such that theopposite end of the target numerology in the frequency domain is withinthe opposite end of the passband; the second filter which filters anoutput of the second mixer to attenuate any signal past the opposite endof the passband; and a third mixer which frequency rotates an output ofthe second filter such that the target numerology returns to itsoriginal location in the input signal in the frequency domain.

The steps and/or operations described above in relation to an embodimentof the present disclosure may occur in a different order, or inparallel, or concurrently for different epochs, etc., depending on thespecific embodiment and/or implementation, as would be understood by oneof ordinary skill in the art. Different embodiments may perform actionsin a different order or by different ways or means. As would beunderstood by one of ordinary skill in the art, some drawings aresimplified representations of the actions performed, their descriptionsherein simplified overviews, and real-world implementations would bemuch more complex, require more stages and/or components, and would alsovary depending on the requirements of the particular implementation.Being simplified representations, these drawings do not show otherrequired steps as these may be known and understood by one of ordinaryskill in the art and may not be pertinent and/or helpful to the presentdescription.

Similarly, some drawings are simplified block diagrams showing onlypertinent components, and some of these components merely represent afunction and/or operation well-known in the field, rather than an actualpiece of hardware, as would be understood by one of ordinary skill inthe art. In such cases, some or all of the components/modules may beimplemented or provided in a variety and/or combinations of manners,such as at least partially in firmware and/or hardware, including, butnot limited to one or more application-specific integrated circuits(“ASICs”), standard integrated circuits, controllers executingappropriate instructions, and including microcontrollers and/or embeddedcontrollers, field-programmable gate arrays (“FPGAs”), complexprogrammable logic devices (“CPLDs”), and the like. Some or all of thesystem components and/or data structures may also be stored as contents(e.g., as executable or other machine-readable software instructions orstructured data) on a non-transitory computer-readable medium (e.g., asa hard disk; a memory; a computer network or cellular wireless networkor other data transmission medium; or a portable media article to beread by an appropriate drive or via an appropriate connection, such as aDVD or flash memory device) so as to enable or configure thecomputer-readable medium and/or one or more associated computing systemsor devices to execute or otherwise use or provide the contents toperform at least some of the described techniques.

One or more processors, simple microcontrollers, controllers, and thelike, whether alone or in a multi-processing arrangement, may beemployed to execute sequences of instructions stored on non-transitorycomputer-readable media to implement embodiments of the presentdisclosure. In some embodiments, hard-wired circuitry may be used inplace of or in combination with software instructions. Thus, embodimentsof the present disclosure are not limited to any specific combination ofhardware circuitry, firmware, and/or software.

The term “computer-readable medium” as used herein refers to any mediumthat stores instructions which may be provided to a processor forexecution. Such a medium may take many forms, including but not limitedto, non-volatile and volatile media. Common forms of non-transitorycomputer-readable media include, for example, a floppy disk, a flexibledisk, hard disk, magnetic tape, or any other magnetic medium, a CD-ROM,any other optical medium, punch cards, paper tape, any other physicalmedium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM,any other memory chip or cartridge, or any other medium on whichinstructions which can be executed by a processor are stored.

Some embodiments of the present disclosure may be implemented, at leastin part, on a portable device. “Portable device” and/or “mobile device”as used herein refers to any portable or movable electronic devicehaving the capability of receiving wireless signals, including, but notlimited to, multimedia players, communication devices, computingdevices, navigating devices, etc. Thus, mobile devices include (but arenot limited to) user equipment (UE), laptops, tablet computers, portabledigital assistants (PDAs), mp3 players, handheld PCs, instant messagingdevices (IMD), cellular telephones, global navigational satellite system(GNSS) receivers, watches, or any such device which can be worn and/orcarried on one's person.

Various embodiments of the present disclosure may be implemented in anintegrated circuit (IC), also called a microchip, silicon chip, computerchip, or just “a chip,” as would be understood by one of ordinary skillin the art, in view of the present disclosure. Such an IC may be, forexample, a broadband and/or baseband modem chip.

While several embodiments have been described, it will be understoodthat various modifications can be made without departing from the scopeof the present disclosure. Thus, it will be apparent to those ofordinary skill in the art that the present disclosure is not limited toany of the embodiments described herein, but rather has a coveragedefined only by the appended claims and their equivalents.

What is claimed is:
 1. A method, comprising: (a) performing a firstmixing of an input signal with a digital carrier which frequency rotatesthe input signal such that one end of a target bandwidth in the inputsignal is aligned with a corresponding edge of a passband of a firstbandpass filter; (b) performing, by the first bandpass filter, a firstfiltering on the first mixed input signal; (c) performing a secondmixing of the first filtered input signal with a digital carrier whichfrequency rotates the first filtered input signal such that the oppositeend of the target bandwidth is aligned with a corresponding edge of apassband of a second bandpass filter; (d) performing, by the secondbandpass filter, a second filtering on the second mixed input signal;and (e) performing a third mixing on the second filtered input signalwhich frequency rotates the second filtered input signal such that thetarget bandwidth returns to the target bandwidth in the input signalprior to the first mixing; wherein the target bandwidth comprises atarget numerology, and wherein, when the target numerology is less thana minimum target numerology threshold for the passband of the firstbandpass filter, further comprising repeating the steps starting withstep (a) and using the minimum target numerology threshold as thepassband for the first bandpass filter and the second bandpass filter.2. The method of claim 1, further comprising: outputting the third mixedinput signal as the target bandwidth.
 3. The method of claim 1, whereinperforming the first mixing of an input signal and performing the secondmixing of the first filtered input signal each separates the targetbandwidth from the input signal and reduces inter-carrier interference(ICI).
 4. The method of claim 1, wherein the input signal is from atelecommunications system using at least one of orthogonal frequencydivision multiplex (OFDM) symbols and non-OFDM symbols.
 5. The method ofclaim 1, wherein the input signal is from a 3^(rd) GenerationPartnership Project (3GPP) new radio (NR) telecommunications system. 6.The method of claim 1, wherein the input signal has mixed numerologies,the target bandwidth may be any one among the mixed numerologies, andthe passband of the first bandpass filter is greater than or equal to abandwidth of a largest target numerology bandwidth which may bereceived.
 7. The method of claim 1, wherein performing the third mixingfurther comprises: removing a ½ subcarrier frequency offset.
 8. Themethod of claim 1, wherein the first bandpass filter and the secondbandpass filter are hard-wired fixed bandwidth filters.
 9. The method ofclaim 1, further comprising, before performing the first mixing:sampling a received signal with mixed numerologies to output the sampledsignal as the input signal for the first mixing.
 10. The method of claim9, further comprising: outputting the third mixed input signal as thetarget numerology when the target numerology is greater than or equal toa minimum target numerology threshold for the passband of the secondbandpass filter.